DE102015114849B4 - Process for the production of light-emitting diode filaments and light-emitting diode filament - Google Patents

Abstract

Method for producing light-emitting diode filaments (10) with the following steps in the given order: A) applying a large number of light-emitting diode chips (3) directly to a first carrier (1), B) covering the light-emitting diode chips (3) with a second carrier (2 ),C) Overmoulding of the light-emitting diode chips (3) with a casting body (4) to form a coherent filament assembly (40), with the two carriers (1, 2) serving as molds and with the casting body (4) being attached directly to the light-emitting diode chips (3) is formed,D) removing only the first carrier (1) or only the second carrier (2),E) attaching electrical connections (5) to the potting body (4) and between the light-emitting diode chips (3), so that the light-emitting diode chips (3 ) are electrically connected, E1) attaching at least one phosphor body (8) to the filament assembly (40), E2) removing the carrier (1, 2) remaining in step D), and F) separating the filament assembly (40) to form the light-emitting diode filaments (10 ),wobe i each of the finished light-emitting diode filaments (10) is mechanically self-supporting, comprises at least 8 of the light-emitting diode chips (3) and has a length-to-width ratio of at least 15, and- the finished light-emitting diode filaments (10) emit light on opposite main sides (11, 12). emit.

Description

A method for producing light-emitting diode filaments is specified. In addition, a light-emitting diode filament is specified.

Document US 2014/0 369 036 A1 relates to an LED lamp and a filament with such a lamp.

The pamphlet DE 10 2007 009 351 A1 relates to a light source in which LED units are attached to a common carrier.

Document US 2009/0 173 954 A1 relates to a semiconductor arrangement in which a multiplicity of semiconductor elements are embedded in a matrix material.

The publication WO 2007/149 362 A2 relates to an LED arrangement in which LED units are embedded in an electrically insulating material.

One problem to be solved is to specify a method with which light-emitting diode filaments can be produced efficiently.

This object is achieved, inter alia, by a method having the features of patent claim 1 . Preferred developments are the subject matter of the dependent claims.

A light-emitting diode filament is produced with the method. The light-emitting diode filament is, in particular, a lamp component that is modeled on a filament of a conventional incandescent lamp. The light-emitting diode filament is about a strip that is provided with several light-emitting diode chips and emits white, visible light during operation. The light-emitting diode filament is preferably set up to be used in a simulation of an incandescent lamp and/or to simulate an incandescent wire.

The method includes the step of applying a multiplicity of light-emitting diode chips to a first carrier. The light-emitting diode chips are preferably applied directly to the first carrier. The first carrier can be a temporary or a permanent carrier for the light-emitting diode chips. The light-emitting diode chips can all be structurally identical. Alternatively and preferably, at least two or at least three different types of light-emitting diode chips are used. For example, blue light-emitting diode chips are used to excite a phosphor in combination with light-emitting diode chips emitting red light. Likewise, first blue-emitting light-emitting diode chips for exciting a phosphor, second blue-emitting light-emitting diode chips for emitting blue light from the light-emitting diode filament and additional red light-emitting light-emitting diode chips can be applied to the carrier, in particular in an alternating sequence.

The method includes the step of covering the light-emitting diode chips with a second carrier. The second carrier is preferably a temporary carrier which is no longer present in the finished light-emitting diode filaments.

In accordance with at least one embodiment, the light-emitting diode chips are placed in a two-dimensional arrangement between the two carriers. In this case, the light-emitting diode chips are preferably provided for a multiplicity of light-emitting diode filaments and not just for a single light-emitting diode filament.

The light-emitting diode chips are overmoulded with a potting body. A cohesive filament composite is created by overmoulding the LED chips. All light-emitting diode chips are preferably mechanically integrated in the filament assembly. In other words, as part of the manufacturing process, the light-emitting diode chips can then be handled as a mechanical unit and also as an organizational unit. The filament composite can also be referred to as an artificial wafer.

The two carriers, between which the light-emitting diode chips are attached, serve as a mold for the cast body. In other words, an outer shape of the potting body is then determined by an interface between a potting compound for the potting body and the supports. In this case, it is possible for the carriers, for example, to line the inner walls of a further, outer mold.

The potting body is created directly on the light-emitting diode chips. In other words, the potting body directly encloses the light-emitting diode chips and is molded onto the light-emitting diode chips. In particular, the potting body is attached to the light-emitting diode chips in such a way that the potting body does not become detached from the light-emitting diode chips when the finished light-emitting diode filaments are used as intended.

The method includes the step of removing both carriers. It is possible for one of the carriers to be removed first and the second carrier only at a later stage of the process.

In the method, electrical connections are attached to the potting body and between the light-emitting diode chips. The light-emitting diode chips are electrically interconnected by the electrical connections, at least within one of the subsequent, finished light-emitting diode filaments. The electrical connections can include, for example, connection areas for external electrical contacting of the finished light-emitting diode filaments and conductor tracks or electrical bridges between adjacent light-emitting diode chips and between light-emitting diode chips and the external electrical contact areas.

The method includes the step of separating the filament assembly into the light-emitting diode filaments. This process step is preferably a last process step of the production process. In particular, a functional test of the light-emitting diode filaments can still be carried out in the filament assembly before they are separated.

Each of the finished light-emitting diode filaments is mechanically self-supporting. In other words, it is then not necessary for the light-emitting diode filaments to be provided later with a mechanical carrier substrate or to be applied to a mechanical carrier substrate. In particular, the light-emitting diode filaments can thus be attached to two electrical and/or thermal contact points and bridge a gap between these contact points without further support or extend away from the contact points.

The light-emitting diode filament comprises at least eight or twelve or 20 of the light-emitting diode chips. Alternatively or additionally, the number of light-emitting diode chips is at most 100 or 50 or 30 or 25.

In accordance with at least one embodiment, the finished light-emitting diode filament has an elongated shape. A length-to-width ratio of the finished light-emitting diode filament is at least 15 or 25. Alternatively or additionally, this length-to-width ratio is at most 80 or 60 or 40.

1. A) Aufbringen einer Vielzahl von Leuchtdiodenchips direkt auf einen ersten Träger,
2. B) Abdecken der Leuchtdiodenchips mit einem zweiten Träger,
3. C) Umspritzen der Leuchtdiodenchips mit einem Vergusskörper zu einem zusammenhängenden Filamentverbund, wobei die beiden Träger als Gussformen oder Teil von Gussformen dienen und wobei der Vergusskörper direkt an die Leuchtdiodenchips angeformt wird,
4. D) Entfernen des ersten Trägers oder des zweiten Trägers oder von beiden Trägern von den Leuchtdiodenchips und von dem Vergusskörper,
5. E) Anbringen von elektrischen Verbindungen an den Vergusskörper und zwischen den Leuchtdiodenchips, sodass die Leuchtdiodenchips elektrisch verschaltet werden, und
6. F) Vereinzeln des Filamentverbunds zu den

The method is set up for the production of light-emitting diode filaments and comprises at least the following steps, in the order given:

1. A) applying a large number of light-emitting diode chips directly to a first carrier,
2. B) covering the light-emitting diode chips with a second carrier,
3. C) Overmoulding the LED chips with a potting body to form a coherent filament composite, with the two carriers serving as molds or part of molds and with the potting body being molded directly onto the LED chips,
4. D) removing the first carrier or the second carrier or both carriers from the light-emitting diode chips and from the potting body,
5. E) attaching electrical connections to the potting body and between the light-emitting diode chips, so that the light-emitting diode chips are electrically connected, and
6. F) Separation of the filament composite to the

Light emitting diode filaments, wherein each of the finished light emitting diode filaments is mechanically self-supporting, comprises at least eight of the light emitting diode chips, and has a length to width ratio of at least 15.

In general lighting, light-emitting diode filaments are increasingly being used, particularly in the production of retrofits, i.e. the simulation of incandescent lamps. In this case, a large number of light-emitting diode chips are arranged on a linear, common substrate and encased with a phosphor material. When switched on, such an arrangement looks like a classic, glowing filament of an incandescent lamp to an observer and thus also represents an important design component of a corresponding product.

However, the production of previously known light-emitting diode filaments is associated with comparatively great effort. So far, light-emitting diode filaments have usually been produced by sawing glass or sapphire into strips. A metal-glass connection is then established so that an electrical connection is established between the contact surfaces and the carrier strip. In this case, a type of leadframe is produced, in particular by mechanical bending or clasping, optionally with prior application of adhesive. The light-emitting diode chips are then applied to this metal-glass composite and the light-emitting diode chips are wired. Subsequently, the phosphor material is applied to each of the filaments.

With the method described here, however, it is possible to process the light-emitting diode filaments together in a filament composite. In particular, a fragile glass substrate or sapphire substrate can be dispensed with and the efficiency of the manufacturing process can be increased, as can the yield of the process.

In process step D) only one of the carriers is removed. In a further method step E2) immediately before step F), the remaining carrier is removed. In the finished light-emitting diode filaments, therefore, none of the carriers that are attached in method steps A) and B) are present.

Step E) is followed by a step E1). In this step, at least one phosphor body is applied to the filament assembly. The phosphor body may be one piece and/or continuous and/or extend over at least some of the filaments. This means that the luminescent body can cover the filament assembly and in particular the potting body for the most part or over the entire surface, seen in plan view. The phosphor body can be applied as a film or as a plate, or it can also be formed by printing or spraying onto the casting body and onto the filament assembly from step E).

In accordance with at least one embodiment, the finished light-emitting diode filaments each have exactly one linear arrangement of the light-emitting diode chips. In other words, all the light-emitting diode chips of the light-emitting diode filament are then on a common straight line. Alternatively, it is possible for the light-emitting diode chips to be arranged in two straight lines and for example to be electrically connected in a U-shape.

According to at least one embodiment, all the light-emitting diode chips of the finished light-emitting diode filament are electrically connected in series. Alternatively, there can also be a plurality of series circuits connected in parallel within a finished light-emitting diode filament.

According to at least one embodiment, a continuous phosphor body is applied to both main sides of the filament assembly in step E1). In other words, both main sides of the filament assembly are then covered with a phosphor body. In this case, it is possible for the phosphor body or bodies to completely cover the filament assembly, with the exception of electrical contact surfaces for external electrical contacting of the finished light-emitting diode filaments.

The finished light-emitting diode filaments emit the light on two opposite sides. The emitted light is preferably white light. Within the scope of manufacturing tolerances, the finished light-emitting diode filaments preferably emit light of the same color on both sides.

According to at least one embodiment, the first carrier is a permanent carrier that is still present in the finished light-emitting diode filaments. In other words, as part of the manufacturing process, only the second carrier is then removed in the course of the manufacturing process. The first, permanent carrier is, for example, a heat sink, a phosphor layer or an optical plate, for example with lenses.

According to at least one embodiment, the first, preferably permanent carrier in the finished light-emitting diode filaments extends completely over a filament underside. Furthermore, a filament upper side opposite the filament lower side is preferably only partially covered by a luminescent body. In particular, only the external electrical contact surfaces are left free of the phosphor body.

According to at least one embodiment, the finished light-emitting diode filaments are mechanically flexible. This can be achieved in particular by the potting body. The fact that the finished light-emitting diode filaments are mechanically flexible can mean that, when used as intended, they can be bent once or several times with a radius of curvature that is less than or equal to the length of the finished light-emitting diode filaments. In this case, the potting body is preferably made from a mechanically flexible plastic and a mechanical connection between the individual light-emitting diode chips occurs at least partially via the potting body.

As an alternative or in addition to bending, it is also possible for the finished light-emitting diode filaments to be twisted. For example, a rotation angle along a longitudinal axis along which the finished light-emitting diode filaments can be twisted non-destructively once or several times, temporarily or permanently, is at least 45° or 90° or 120°. Such light-emitting diode filaments that can be twisted make it possible to achieve particularly uniform radiation on all sides in a simulation of an incandescent lamp. The twisting of the light-emitting diode filaments is made possible in particular by the use of the potting body, in comparison to a rigid carrier, for example made of glass or sapphire.

According to at least one embodiment, one or more heat sinks are integrated in each of the light-emitting diode filaments. Heat sink means, for example, that a thermal conductivity of a material of the heat sink is at least 50 W/m·K or at least 100 W/m·K or 120 W/m·K. In particular, the heat sink is formed from a thermally conductive metal such as aluminum and/or copper or consists predominantly of this.

According to at least one embodiment, the heat sink is electrically isolated from the electrical connections. This makes it possible to carry out thermal contacting of the finished light-emitting diode filaments independently of electrical contacting. In particular, the light-emitting diode filament can then have large-area thermal contact areas, for example with an area of at least 5 mm ² each.

According to at least one embodiment, the heat sink and/or thermal contact surfaces on the one hand and the electrical contact surfaces for external electrical contacting on the other hand are located in the finished light-emitting diode filaments on opposite main sides. In particular, the electrical contact surfaces are on the top side of the filament and the heat sink and/or the thermal contact surfaces are on the bottom side of the filament.

In accordance with at least one embodiment, the heat sink is formed by a continuous layer that is located in a plane below the potting body and the light-emitting diode chip. In other words, the heat sink is then attached to the light-emitting diode chips, for example in the form of the first carrier, and the light-emitting diode chips then rest on the heat sink.

In accordance with at least one embodiment, the heat sink comprises or consists of a shadow mask. In this case, one or more of the light-emitting diode chips is preferably placed in each hole of the shadow mask in step A). In other words, the light-emitting diode chips and the heat sink or at least the perforated mask then lie in a common plane.

In accordance with at least one embodiment, a fixed mechanical connection between the light-emitting diode chips and the perforated mask is produced in step C) by creating the potting body. This means that a material of the potting body can then be filled into each hole of the shadow mask with a light-emitting diode chip, so that the light-emitting diode chips are fitted into the holes via the potting body and fastened.

In accordance with at least one embodiment, the potting body completely covers the heat sink and in particular the perforated mask, seen in plan view. This means that a thickness of the potting body then preferably exceeds a thickness of the perforated mask. In particular, the potting body protrudes beyond the shadow mask on only one side and terminates flush with the shadow mask on a further side, preferably on the underside of the filament.

According to at least one embodiment, the heat sink includes a base plate in addition to the shadow mask. The shadow mask is preferably attached directly to the base plate. It is possible for the bottom plate and the shadow mask to be designed in one piece. The base plate is preferably free of recesses or openings through the base plate, so that the base plate can form a coherent, solid and uninterrupted layer. Here, the potting body can cover the base plate completely, seen in plan view.

In accordance with at least one embodiment, the carriers cover or at least one of the carriers only partially covers the main sides of the light-emitting diode chips in step C). In other words, the main sides of the light-emitting diode chips are then partially exposed. This makes it possible for the potting body to also be formed in places on the main sides of the light-emitting diode chips. In this way, anchoring structures can be formed, by means of which the light-emitting diode chips can be better mechanically integrated into the potting body and/or the filament assembly.

According to at least one embodiment, the light-emitting diode chips are applied alternately to the first carrier in step H). This can mean that the light-emitting diode chips alternately have an n-side and a p-side at the top. The light-emitting diode chips are thus applied alternately rotated by 180° in relation to one another. Alternatively, it is possible that there is also a rotation of just 90° between adjacent light-emitting diode chips, for example in order to achieve emission from all sides of the finished light-emitting diode filaments.

According to at least one embodiment, the finished light-emitting diode filaments have a length of at least 15 mm or 20 mm or 30 mm. Alternatively or additionally, the length of the finished light-emitting diode filaments is at most 100 mm or 60 mm or 45 mm.

According to at least one embodiment, a width or average width of the light-emitting diode filaments is at least 0.5 mm or 0.8 mm or 1.1 mm. Alternatively or additionally, the width is at most 5 mm or 3 mm or 2 mm or 1.8 mm. The width is preferably determined in the direction parallel to the main sides of the carrier. The width of the finished light-emitting diode filaments is thus determined in particular by the separation in step F).

According to at least one embodiment, the light-emitting diode filaments have a thickness of at least 0.6 mm or 0.8 mm or 1.2 mm. Alternatively or additionally, the thickness is max at least 3 mm or 2 mm or 1.6 mm. The thickness is preferably not influenced or not significantly influenced in step F).

In accordance with at least one embodiment, the heat sink has a thickness of at least 0.15 mm or 0.2 mm or 0.3 mm. Alternatively or additionally, the thickness of the heat sink is at most 1 mm or 0.8 mm or 0.5 mm. In this case, a main component of the heat sink is preferably a metal such as copper or aluminum. Main component means that the total weight proportion of the corresponding substance in the heat sink is at least 60% or 80% or 95%.

According to at least one embodiment, the finished light-emitting diode filaments are free of a glass substrate or a sapphire substrate. This does not preclude the individual light-emitting diode chips from having a sapphire carrier, but such a sapphire carrier does not extend over the entire light-emitting diode filament and is not or not significantly decisive for mechanical stabilization of the light-emitting diode filament overall.

According to at least one embodiment, the finished light-emitting diode filaments are designed to be inserted or clamped into an external holding device. In this way, the light-emitting diode filaments can be electrically and/or thermally contacted externally.

According to at least one embodiment, the potting body includes particles or admixtures to improve thermal conductivity. For example, the potting body then contains particles of a metal oxide such as titanium dioxide or zirconium dioxide or tantalum oxide. The potting body can also have metal particles or coated metal particles. The particles can be spherical or polyhedral in shape or in the form of elongated threads.

According to at least one embodiment, the potting body is reflective for visible light. In particular, the potting body appears white to an observer.

In accordance with at least one embodiment, the potting body contains at least one phosphor. It is possible for the potting body to contain the same phosphor as the phosphor body and/or the phosphor layer. This makes it possible for radiation exiting laterally from the light-emitting diode chips not to be reflected at the potting body, but instead to be converted as in the phosphor body and/or in the phosphor layer. For the light generated by the phosphor, the potting body is preferably designed to be transparent or scattering.

According to at least one embodiment, the potting body is permeable to visible light, in particular clear and transparent. Alternatively, the potting body may appear milky.

In addition, a light-emitting diode filament is specified. The light emitting diode filament is preferably manufactured using a method as specified in connection with one or more of the embodiments given above. Features of the method are therefore also disclosed for the light-emitting diode filament and vice versa.

In at least one embodiment, the light-emitting diode filament is designed to be used in a light bulb replacement as a simulation of a glow wire. An intended operating voltage of the light-emitting diode filament is preferably at least 30 V or 45 V or 60 V and/or at most 400 V or 240 V or 115 V or 90 V or 80 V.

A method described here and a light-emitting diode filament described here are explained in more detail below with reference to the drawing using examples and exemplary embodiments. The same reference symbols indicate the same elements in the individual figures. However, no references to scale are shown here; on the contrary, individual elements may be shown in an exaggerated size for better understanding.

• 1 bis 8 schematische Darstellungen von Beispielen zur Erläuterung von Teilaspekten des hier beschriebenen Verfahrens zur Herstellung von hier beschriebenen Leuchtdiodenfilamenten.

Show it:

• 1 until 8th schematic representations of examples to explain partial aspects of the method described here for the production of light-emitting diode filaments described here.

In 1A 1 is a schematic sectional representation of a method step of a method for the production of light-emitting diode filaments 10 described here. A plurality of light-emitting diode chips 3 are mounted on a first carrier 1 . The carrier 1 is, for example, a mechanically flexible film or else a rigid substrate. The light-emitting diode chips 3 each have a chip substrate 33 on which a semiconductor layer sequence 30 is attached. According to 1A all n-sides 31 point towards the first carrier 1 and all p-sides 32 point away from the first carrier 1.

Deviating from 1A different types of light-emitting diode chips 3 can also be used. In the 1A The light-emitting diode chips 3 shown each have a light-transmitting chip substrate 33, for example made of sapphire, and can therefore emit radiation on all sides. The semiconductor layer sequence 30 is preferably based on AlInGaN, so that the light-emitting diode chips 3 are set up, for example, to generate blue light.

In the process step, as in 1B shown, a second carrier 2 is applied to the light-emitting diode chip 3 . A volume is sealed off by the second carrier 2, which is a film, for example, so that a potting body 4 can be produced in the subsequent method step.

In 1C1 is in a sectional view and in 1C2 the creation of the potting body 4 is illustrated in a schematic plan view. The potting body 4 is made from a silicone, epoxy or silicone-epoxy hybrid material, for example. The potting body 4 can have an admixture, for example to adjust thermal conductivity or to adjust optical properties. In the example of 1 the potting body 4 appears white to an observer and is reflective to visible light. Alternatively, the potting body 4 can be provided with a phosphor and otherwise be translucent. A phosphor in the potting body 4 allows lateral emission of the light-emitting diode chips 3, ie emission in particular along the longitudinal axis of the light-emitting diode filament 10, to be converted directly into light of a different wavelength.

In 1C2 it can be seen that the light-emitting diode chips 3 are arranged two-dimensionally. All of the light-emitting diode chips 3 are mechanically connected via the potting body 4 . In this case, the light-emitting diode chips 3 are set up for a large number of the light-emitting diode filaments 10 . A filament composite 40 is thus also produced by the potting body 4 . The filament assembly 40 is an artificial wafer with which the subsequent light-emitting diode filaments 10 to be separated can be handled together.

According to the sectional view in 1D1 and the plan view in 1D2 the two carriers 1, 2 are removed. An external electrical contact surface 55 is produced in strip form at the ends of the subsequent, finished light-emitting diode filaments 10 . The contact surface 55 is produced, for example, by sticking on a printed circuit board foil, by screen printing, by paste printing, by jetting or by electroplating.

Contrary to what is shown, it is not necessary for the contact surface 55 to extend as a continuous strip over several of the subsequent light-emitting diode filaments 10 . In the process step, as in the 1E1 and 1E2 shown, the light-emitting diode chips 3 are electrically connected to the contact areas 55 and to one another via electrical connections 5 . The electrical connections 5 are bonding wires. Instead of bonding wires, planar connections such as conductor tracks can also be applied, for example by means of photo technology or screen printing or jetting. Corresponding electrical connections 5 can also be vapour-deposited.

As in the sectional view in 1F1 and in plan view in 1F2 shown, phosphor bodies 8 are applied both to a filament underside 11 and to a filament upper side 12, on which the electrical connections 5 and the contact surfaces 55 are located. The phosphor bodies 8 preferably each leave an edge region free on the contact surfaces 55, both on the filament underside 11 and on the filament upper side 12.

The phosphor body 8 on the underside 11 of the filament is, for example, a silicone film or else a glass plate to which a phosphor or a phosphor mixture is added. This can also apply to the phosphor body 8 on the filament top 12 . Alternatively, the phosphor body 8 is produced on the filament top 12 by imprinting or transfer molding or injection molding, analogously to the potting body 4.

Furthermore, it is possible for the two phosphor bodies 8 to be replaced by a single phosphor coating (not shown). Such a phosphor coating, which can also be present in all other examples as an alternative or in addition to the phosphor body 8 or the phosphor layer 7, can be produced, for example, by immersing the filament in a bath of converter material or by dispensing. With such a phosphor coating, cylindrical or almost cylindrical light-emitting diode filaments 10 can be realized, in particular with uniform emission in all directions transverse to a longitudinal axis of the light-emitting diode filament 10 .

As in all other examples, it is possible to provide one or more transparent protective layers instead of the phosphor body or bodies 8, which then have no wavelength-changing properties.

The separation towards the finished light-emitting diode filaments 10 is shown in the sectional view in 1G1 and in plan view in 1G2 illustrated. The resulting light-emitting diode filaments 10 are mechanically self-supporting and can be mechanically flexible or rigid. The separating into the light-emitting diode filaments 10 takes place, for example, by sawing or by scoring together with breaking, by stamping or by a laser cutting process.

With this method, the light-emitting diode chips 3 can be integrated into the filament assembly 40, with the filament assembly 40 being an artificial wafer in which the processing can take place efficiently at panel level. A potting body 4 of this type for the filament composite 40 can be produced cost-effectively and its mechanical properties can be adjusted by suitably selecting the material for the potting body 4 . In particular, because of the potting body 4, comparatively time-consuming, expensive and fracture-prone process steps such as sawing glass and producing metal-glass contacts with conventional light-emitting diode filaments can be dispensed with. Furthermore, high mechanical stability and high dimensional accuracy can be achieved during processing, compared to the fragile metal-glass leadframe composites that have been customary up to now. The application of the phosphor element 8 while still in the filament assembly 40 is also possible.

In 2 Another example of the manufacturing process is illustrated in sectional views. Deviating from 1 the light-emitting diode chips 3 are attached to the first carrier 1 alternately with an n-side 31 and a p-side 32 . As a result, a bidirectional or omnidirectional emission similar to a glow wire in an incandescent lamp can be realized in the later, finished light-emitting diode filaments 10 . According to 2 B the second carrier 2 is attached and according to 2C the potting body 4 and the filament composite 40 are produced.

In the 2D and 2E the electrical circuitry of the light-emitting diode chips 3 is shown. In doing so, see 2E , two series circuits realized. In a series connection, all the light-emitting diode chips 3 are located with the p-side 32 facing up, and in a second series connection, all the light-emitting diode chips 3 are located with the p-side 32 facing down. Intermediate light-emitting diode chips 3 that are not addressed in a series circuit are bridged with the electrical connections 5a, which can be in the form of conductor tracks. This is possible because the chip substrates 33 are formed from an electrically insulating material or have an electrically insulating coating. In this case, the electrical connections 5a preferably completely cover the associated light-emitting diode chips 3, seen in a plan view.

Unlike in 2E shown, it is possible for a through-contact to be provided through the potting body 4 at one end of the light-emitting diode filament 10 . As a result, the series circuit on the filament top 12 can be electrically connected in series with the series circuit on the filament bottom 11, so that the contact surfaces 55 can then be located at a single end of the light-emitting diode filament 10, with one of the only two external electrical contact surfaces in this case then being connected the filament underside 11 and another of the contact surfaces 55 is attached to the filament top 12 .

Analogous to 1 the light-emitting diode chips 3 are each provided with a single, coherent phosphor body 8 on the filament underside 11 and on the filament upper side 12 .

As in all other exemplary embodiments and examples, the at least one phosphor body 8 preferably has a homogeneous material composition and a uniform thickness. Alternatively, it is possible for the phosphor body 8 to be applied in alternating thicknesses, so that there are thinner regions of the phosphor body 8 between adjacent light-emitting diode chips 3 , for example. Alternatively, at least one of the phosphor bodies 8 or both phosphor bodies 8 can be configured in a lens-shaped manner in some areas, with each of the light-emitting diode chips 3 then preferably being assigned a lens section.

In 3 Another example is shown. The process steps of 3A until 3D are analogous to 1 . In the process step 3F a heat sink 6 is applied to the entire surface of the filament underside 11 . The heat sink 6 is formed from aluminum, for example, and preferably has a thickness of at least 150 μm. Likewise, the heat sink 6 can function as a mirror for the radiation generated in the light-emitting diode chips 3 . In this case, the finished light-emitting diode filament 10 emits radiation only on the filament top 12 and not on the filament bottom 11. The further process steps of FIG 3F and 3G are analogous to 1 .

Such a heat sink 6 enables improved heat removal and cooling of the light-emitting diode chips 3 to be implemented. Furthermore, such a heat sink 6 can be thermally connected to an external cooling plate at least at certain points.

According to 3 the heat sink 6 is located below the potting body 4. In the example, as in 4 illustrated, the heat sink 6 is designed as a shadow mask 61 . According to 4A one of the light-emitting diode chips 3 is placed in each hole of the shadow mask 61 in the areas for the light-emitting diode filaments 10 .

In the next step, see 4B , the holes are filled with the casting body 4, so that the filament composite 40 is formed. The heat sink 6 ends flush with the perforated mask 61 on the underside of the filament 11 (not shown). On the filament top 12, the potting body 4, as in the other examples, is flush with a main side of the light-emitting diode chips 3 and thus protrudes beyond the shadow mask 61. This preferably does not apply to an edge of the later, finished light-emitting diode filaments 10, so that the finished light-emitting diode filaments 10 can be thermally contacted via the perforated mask 6.

In the next step of the process, see 4C , the electrical contact surfaces 55 are attached. In this case, the contact surfaces 55 are preferably located in each case between two adjacent regions of the heat sink 6 at the edge. The contact surfaces 55 can protrude further in the direction of the light-emitting diode chips 3 than the exposed areas of the heat sink 6.

In 4D shows that the light-emitting diode chips 3 are electrically connected to the connecting means 5. According to 4E the phosphor body 8 is produced. According to 4F1 separation takes place. The resulting light-emitting diode filament 10 is in 1F2 shown in a plan view.

At the heat sink of 4 good heat dissipation as well as two-sided or omnidirectional radiation can be achieved. Furthermore, the electrical contacts and the thermal external contacts are separated from each other.

In 5 are shown schematically various configurations of the shadow mask 61, as in connection with FIG 4 usable. According to the sectional view in 5A the shadow mask 61 has a smaller thickness than the light-emitting diode chips 3 and, within the scope of manufacturing tolerances, the shadow mask 61 is provided with vertical side walls. In this case, the potting body 4 is preferably designed to be reflective and white.

In the example of the sectional view in 5B the side walls of the shadow mask 61 are arranged inclined to the side faces of the light-emitting diode chips 3 . In the case of a radiation-transmissive, clear-sighted potting body 4, the side walls of the perforated mask 61 can serve as reflectors in order to enable the light to be emitted in a more directed manner.

In the sectional view according to 5C shows that the heat sink 6 has the shadow mask 61 and also a base plate 62 . The light-emitting diode chips 3 are seated on the base plate 62 . As a result, particularly efficient cooling can be implemented. The mechanical properties of the light-emitting diode filament 10 are then essentially determined by the heat sink 6 . For example, in the case of a mechanically flexible, self-supporting film for the heat sink 6, the associated light-emitting diode filament 10 can also be implemented in a mechanically flexible manner.

In the plan view in 5D it is shown that separating slots 69 can be present in areas between adjacent light-emitting diode filaments 10 . Splitting and separating towards the light-emitting diode filaments 10 then preferably takes place along these separating slits 69. The separating slits 69 can have different shapes, seen in plan view, as in FIG 5D illustrated.

In the 4 and 5 the holes in the shadow mask 61 are each square or rectangular in shape when viewed in plan. Deviating from this, round holes can also be used, viewed from above. This is analogous to, in particular, in the case of reflector-like configurations 5B advantageous.

In the example of the method, as in the sectional views of 6 shown, the heat sink 6 is used as the first carrier 1 . The first carrier 1 thus remains permanently in the light-emitting diode filament 10. The remaining method steps are, for example, analogous to FIG 1 accomplished.

In the example of 7 serves as the first carrier 1 of the luminescent body 8, which also remains permanently on the light-emitting diode chips 3. In this case, the phosphor body 8 is, for example, a glass plate or plastic plate to which the phosphor has been added. Also in the method according to 7 the remaining process steps are preferably analogous to 1 accomplished.

In this procedure, as in the 6 and 7 illustrated, a temporary intermediate carrier can be dispensed with and only a temporary carrier 2 is required overall for sealing when the cast body 4 is produced. In particular, better optical and/or thermal coupling of the first carrier 1 to the light-emitting diode chips 3 can also be implemented.

In the process, as in the sectional views of 8th shown, a mold 9 is used. Due to this mold 9, the two carriers 1, 2 are not applied to the light-emitting diode chips 3 over the entire surface. By this, see 8C , the main sides of the light-emitting diode chips 3 are partially covered by the potting body 4. As a result, anchoring structures 43 are formed on edges of the light-emitting diode chips 3 . About these anchoring structures 43 is an improved mechanical anchorage tion of the light-emitting diode chips 3 compared to the examples of 1 until 7 feasible. Corresponding anchoring structures 43 can also be present in all other examples.

Reference List

1

first carrier

2

second carrier

3

LED chip

30

semiconductor layer sequence

31

n-side

32

p side

33

chip substrate

4

potting body

40

filament composite

43

anchoring structure

5

electrical connection

55

electrical contact surface

6

heat sink

61

shadow mask

62

bottom plate

69

singulation slot

7

phosphor layer

8th

fluorescent body

9

mold

10

light emitting diode filament

11

filament bottom

12

filament top

Claims (14)

Method for producing light-emitting diode filaments (10) with the following steps in the given order: A) applying a large number of light-emitting diode chips (3) directly to a first carrier (1), B) covering the light-emitting diode chips (3) with a second carrier (2), C) Overmoulding the light-emitting diode chips (3) with a potting body (4) to form a coherent filament assembly (40), with the two carriers (1, 2) serving as molds and with the potting body (4) being molded directly onto the light-emitting diode chips (3). , D) removing only the first support (1) or only the second support (2), E) Attaching electrical connections (5) to the potting body (4) and between the light-emitting diode chips (3), so that the light-emitting diode chips (3) are electrically connected, E1) attaching at least one phosphor body (8) to the filament assembly (40), E2) removing the carrier (1, 2) remaining in step D), and F) separating the filament assembly (40) to form the light-emitting diode filaments (10), wherein each of the finished light emitting diode filaments (10) is mechanically self-supporting, comprises at least 8 of the light emitting diode chips (3) and has a length to width ratio of at least 15, and - The finished light-emitting diode filaments (10) emit light on opposite main sides (11, 12). Method according to the preceding claim, wherein the finished light-emitting diode filaments (10) each have exactly one linear arrangement of the light-emitting diode chips (3) and all the light-emitting diode chips (3) of the finished light-emitting diode filaments (10) are electrically connected in series. Method according to one of the preceding claims, in which in step E1) the at least one phosphor body (8) is applied to both main sides of the filament assembly (40). Method according to one of the preceding claims, in which the finished light-emitting diode filaments (10) can be bent non-destructively with a radius of curvature that is less than or equal to the length of the finished light-emitting diode filaments (10), wherein the potting body (4) is made from a mechanically flexible plastic. Procedure according to one of Claims 1 until 3 , in which a heat sink (6) is integrated in each of the light-emitting diode filaments (10), the heat sink (6) being electrically insulated from the electrical connections (5), and the heat sink (6) and electrical contact surfaces (55) being external electrical contacting of the finished LED filaments (10) are located on opposite main sides. Procedure according to one of Claims 1 until 3 , in which a heat sink (6) is integrated in each of the light-emitting diode filaments (10), the heat sink (6) comprising or consisting of a shadow mask (61), wherein in step A) at least one of the Light-emitting diode chip (3) is placed, and in step C) through the casting body (4) a fixed mechanical connection between the light-emitting diode chip (2) and the shadow mask (61) is made and the casting body (4) the hole mask (61), seen in top view, completely covered. Method according to the preceding claim, in which the heat sink (6) comprises a base plate (62) in addition to the perforated mask (61), wherein the perforated mask (61) is mounted on the base plate (62) and the potting body (4) also completely covers the base plate (62), seen in plan view. Method according to one of the preceding claims, in which the carriers (1, 2) in step C) only partially cover the main sides of the light-emitting diode chips (3), so that the potting body (4) is also formed in places on the main sides of the light-emitting diode chips (3) and so Anchoring structures (43) are formed. Method according to one of the preceding claims, in which in step A) the light-emitting diode chips (3) are applied alternately with an n-side (31) and a p-side (32) on top of the first carrier (1). Procedure according to one of Claims 5 until 7 , in which the finished light-emitting diode filaments (10) have a length of between 20 mm and 60 mm, a width of between 0.8 mm and 3 mm and a thickness of between 0.8 mm and 2 mm, with a thickness of the heat sink ( 6) is between 0.2 mm and 0.8 mm inclusive and a main component of the heat sink (6) is copper or aluminium. Method according to one of the preceding claims, in which the finished light-emitting diode filaments (10) are free of a glass support or a sapphire support, the finished light-emitting diode filaments (10) being adapted to be inserted or clamped into an external holding device in order to provide an electrical and thermal to establish external contact. Method according to one of the preceding claims, in which the potting body (4) comprises particles to improve the thermal conductivity of the potting body (4), wherein the potting body (4) has a reflective effect for visible light or is translucent. Method according to one of the preceding claims, in which the potting body (4) comprises at least one phosphor. Light-emitting diode filament (10) which is produced using a method according to one of the preceding claims, wherein the light-emitting diode filament (10) is designed to be used in a light bulb replacement as a replica of a glow wire, wherein an intended operating voltage of the light-emitting diode filament (10) is between 30 V and 400 V inclusive.

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